Cerda Ignacio A, Desojo Julia B, Trotteyn María J, Scheyer Torsten M
Conicet: Rivadavia 1917, Buenos Aires, 1000-1499, Argentina; Instituto de Investigación en Paleobiología y Geología, Universidad Nacional de Río Negro, Museo Carlos Ameghino, Belgrano 1700, Paraje Pichi Ruca (predio Marabunta), 8300, Cipolletti, Río Negro, Argentina.
J Morphol. 2015 Apr;276(4):385-402. doi: 10.1002/jmor.20348. Epub 2015 Feb 2.
Postcranial osteoderms are commonly developed in the major lineages of Archosauriformes, including forms such as proterochampsids and doswelliids. Here, we survey the histology of osteoderms of the doswelliids Archeopelta arborensis and Tarjadia ruthae, and the proterochampsids Chanaresuchus bonapartei and Pseudochampsa ischigualastensis to understand better the morphogenesis of these skeletal elements. Whereas, the Doswelliid osteoderms possess a trilaminar organization, in which two cortices (external and basal) can be differentiated from an internal core of cancellous bone, these elements are compact structures in proterochampsids. The osteoderms of P. ischigualastensis are avascular and they consist entirely of parallel-fibered bone. Conversely, the osteoderms of C. bonapartei are well vascularized structures composed of zones of woven-fibered bone and annuli of parallel-fibered bone. The rather simple microstructure observed in P. ischigualastensis osteoderms suggests that these elements grew at a constant, low rate. Compared with proterochampsids, doswelliid osteoderms possess a more complex histology, which appears to be linked to variations in the growth rate during the osteoderm formation and also to the development of the external ornamentation. A comparison of our findings with the results of earlier studies on other archosauriforms (phytosaurs and pseudosuchians) reveals that the general osteoderm histology of doswelliids bears a closer resemblance to that of phytosaurs and pseudosuchians than the proterochampsid osteoderm microstructure. If all archosauriform osteoderms are homologous structures, the closer resemblance of doswellid osteoderm microstructures to that of phytosaurs and pseudosuchians is in agreement with the hypothesis that doswellids are more closely related to archosaurs than proterochampsids. J. Morphol. 276:385-402, 2015. © 2015 Wiley Periodicals, Inc.
颅后骨皮在主龙形类的主要谱系中普遍发育，包括原鳄类和道氏鳄类等形式。在此，我们研究了道氏鳄类的阿氏古鳄（Archeopelta arborensis）和鲁氏塔氏鳄（Tarjadia ruthae）以及原鳄类的波拿巴查纳鳄（Chanaresuchus bonapartei）和伊斯基瓜拉斯托伪鳄（Pseudochampsa ischigualastensis）的骨皮组织学，以便更好地了解这些骨骼元素的形态发生。虽然道氏鳄类的骨皮具有三层结构，其中两个皮质层（外层和基部）可与松质骨的内部核心区分开来，但在原鳄类中这些元素是致密结构。伊斯基瓜拉斯托伪鳄的骨皮无血管，完全由平行纤维骨组成。相反，波拿巴查纳鳄的骨皮是血管丰富的结构，由编织纤维骨区域和平行纤维骨环组成。在伊斯基瓜拉斯托伪鳄骨皮中观察到的相当简单的微观结构表明这些元素以恒定的低速率生长。与原鳄类相比，道氏鳄类的骨皮具有更复杂的组织学，这似乎与骨皮形成过程中的生长速率变化以及外部纹饰的发育有关。将我们的研究结果与早期对其他主龙形类（植龙类和伪鳄类）的研究结果进行比较发现，道氏鳄类的一般骨皮组织学与植龙类和伪鳄类的更为相似，而不是原鳄类的骨皮微观结构。如果所有主龙形类的骨皮都是同源结构，那么道氏鳄类骨皮微观结构与植龙类和伪鳄类的更相似就与道氏鳄类比原鳄类与主龙类关系更密切的假设一致。《形态学杂志》276:385 - 402，2015年。©2015威利期刊公司
